Question

For the chemical equation SO2(g)+NO2(g)↽−−⇀SO3(g)+NO(g) the equilibrium constant at a certain temperature is 3.80. At this temperature, calculate the number of moles of NO2(g) that must be added to 2.50 mol SO2(g) in order to form 1.00 mol SO3(g) at equilibrium.

Answer 1

Answer:

The initial moles of NO₂ that must be added is 1.18

Explanation:

The equilibrium constant is related to the concentrations of the given compounds in the equilibrium as:

$Kc=\frac{[NO][SO_{3}]}{[NO_{2}][SO_{2}]}$

Let us do the other calculations based on ICE table for equilibrium.

                               $SO_{2}+NO_{2}----->SO_{3}+NO$

Initial (I)                           2.50         a                0

Change(C)                      -x               -x              +x

Equilibrium(E)              2.5-x            a-x              x

Where given that the moles of sulfur trioxide at equilibrium = 1

hence

x = 1

At equilibrium

[SO₂] = 2.5-1 =1.5

[SO₃]=[NO₂]=1

[NO₂]= a-1

Let us put the values in

$Kc=\frac{[NO][SO_{3}]}{[NO_{2}][SO_{2}]}$

$Kc=3.80 = \frac{[1][1]}{[a-1][1.5]}$

$5.7a-5.7 = 1$

a = 1.18